The present invention is related to a hybrid installation for providing electric energy from regenerative energy sources, which features a biogas installation that provides electric energy, and at least one additional energy converter, which provides electric energy and whose releasable power is depending of external influence factors, of the wind supply and/or the sun irradiation in particular, wherein the electric energy of the biogas installation and the electric energy of the at least one additional energy converter are fed into a common mains grid.
Biogas installations have a so-called digester, in which biomass containing waste materials, like sewage sludge, biological waste or food leftovers, liquid manure, solid dung, wood chips or even purposefully grown energy plants like for instance maize, cereals and grass are transformed in a multistage process. In doing so, biogas is generated, whose essential energy-rich constituent is methane. In a block-type thermal power station for instance, the biogas can be used for driving an internal combustion engine which drives a generator. The provided electric energy can be fed into a mains grid, whereas the waste heat of the internal combustion engine can be used for heating a building. Due to the combustion process used for driving the generator, electric energy and heat are always generated at the same time in the operation of a biogas installation, in particular, it is not possible to provide electric energy without generating heat at the same time. The thermal and the electric power of a biogas installation can be released at any time, up to maximum value determined by the dimension of the installation. Provided that there is sufficient biogas, the power of the installation can be increased up to its maximum value within a short time by controlling the internal combustion engine.
Other known energy converters can provide electric energy directly without that a noteworthy waste heat is generated. Among these are wind energy- and photovoltaic installations in particular. However, the availability of the provided electric energy of such energy converters depends of external influence factors, in the cited examples from the wind supply or the sun irradiation, respectively. Depending on circumstances, not any at all or only a fraction of the rated power of such installations can be released for longer periods of time.
Hybrid installations for providing electric energy from regenerative energy sources combine different energy converters. One such biogas installation is known from the German patent application DE 10 2004 046 701 A1. It is denoted as a regenerative energy system and combines a wind energy installation generating electric energy and feeding it into a mains grid with an internal combustion engine that is operated by a fuel made from renewable raw material, like rapeseed oil for instance. The internal combustion engine drives a generator, and by doing so it produces electric energy, which is also fed into the mains grid. The known hybrid installation is essentially intended for supplying isolated systems. In this, the internal combustion engine operated with rapeseed oil substitutes a conventionally driven diesel generator and through this it may improve the environmental compliance. In one embodiment, it is conceived to operate the internal combustion engine with biogas. The heat generated in the operation of the internal combustion engine is not exploited in the known hybrid installation.
From the article “Energieoptimierung an der Verbandskläranlage Hallstättersee” by Hansjörg Schenner, published in the journal “Ökoprojekt Das Fachmagazin für Umweltförderung”, Vol. 1/2006, a waste water treatment installation for purifying waste waters is known that has a large energy demand. In order to cover this energy demand, the biogas generated in the digestion tower of the waste water treatment installation is converted into electric energy with the aid of two micro-turbines on the one hand, and on the other hand, a photovoltaic installation additionally feeds electric energy into the internal electric grid of the waste water treatment installation. The thermal energy produced in the operation of the micro-turbines is integrated into the heat grid of the waste water treatment installation, and is used for heating the installations. Alternatively, the electric energy generated by the micro-turbines can be fed into the public mains as ecological current.
From the document EP 0 822 251 A2, an apparatus for producing biogas with a digester is known. The produced biogas is used to power a block-type thermal power station. The waste heat of the gas engine operated in the block-type thermal power station is supplied to a heat consumer and serves also for heating the digester.
From the document WO 2005/061135 A1, an energy system is known for supplying a plant that processes milk or fish, for instance. The system comprises a biogas installation and a combined energy converter, a Stirling motor for instance, which provides heat and electric energy. The heat is supplied to a hot water tank, and from the same it may be extracted again, for instance in order to heat the biogas installation or a stable for animals, for instance. The electric energy is used for the continuous production of ice in a cooling installation. The ice serves for cooling the products to be processed, the milk or the fish for instance. Additionally required electric energy can be extracted from a grid. It is also conceived to use a fuel cell or a wind energy installation in addition.
From the document DE 10 2004 062 993 A1, a biogas installation is known that features a digester and other functional elements housed in a container, a block-type thermal power station for instance. The biogas installation may feature an electrically powered bottling plant for the produced biogas. In this it is also conceived to use a photovoltaic system to power the electric bottling plant.
From the article “Wind-, Solar- and Biogasanlage in Burg auf Fehmarn” by Günter Dörge, published in “de/der Elektromeister+deutsches Elektrohandwerk”, Vol. 24/90, page 1883-1888, a hybrid installation is known which features a biogas installation with a block-type thermal power station operated with the biogas, a wind energy installation and a solar generator. The hybrid system is situated on the location of a waste water treatment facility, which covers its basic electric load from a public electric mains grid and is in addition powered by the hybrid system. A common operation management system controls the elements of the hybrid system and can cut off or connect individual consumers of the waste water treatment facility, like aerators and pumps, depending of the produced electric power. In case that the electric energy produced by sun, wind and biogas exceeds the own demand of the waste water treatment facility in spite of this adjustment of the demanded power, the excess is supplied into the public mains grid.
Starting from this, it is the objective of the present invention to provide a hybrid installation of the kind mentioned in the beginning, which utilises the applied energy sources more efficiently.